The present invention relates to a tensioner device of an transmission endless flexible member such as a chain and a belt used for transmitting power of a driving shaft of an engine to auxiliary machinery such as a valve moving apparatus or an oil pump to drive it.
Hitherto, a transmission endless flexible member such as a chain or a belt for transmitting power from a drive shaft of an engine has a tensioner device for adjusting tension of the endless flexible member automatically, in order to give a proper tension for transmitting power smoothly and in order to prevent vibration of the endless flexible member caused by change of tension of the endless flexible member owing to change of rotation of the driving shaft.
For example, in a chain tension adjusting apparatus disclosed in Japanese Laid-Open Patent Publication Sho 61-48655, a tension giving member consisting of a plate spring and a plastic plate joined together is brought into contact with a loose side of a chain wound round sprockets attached to a crankshaft and a valve driving cam shaft respectively. The tension giving member has a lower end pivoted to a crankcase and an upper end pivoted to a piston member of a tension adjusting mechanism. The piston member is fitted to a guide hole of a case formed on a cylinder head so as to slide, and forced by a coil spring held by a screw member so as to bent the tension giving member toward the chain for giving tension to the chain.
In the prior art disclosed in the above-mentioned publication, the upper end of the tension giving member for pressing the chain to give tension is supported by the piston member which is movable only in a direction to increase the tension of the chain, because loosing of the chain must be compensated.
Therefore, the above-mentioned tension adjusting mechanism is separated from the engine main body such as a cylinder head and the like, and the coil spring forcing the piston member and the screw member holding the coil spring are necessary, so that the construction for supporting the upper end of the tension giving member requires a large number of parts and is complicated.
The present invention has been accomplished in view of the foregoing, and an object of the inventions is to provide a tensioner device having a small number of parts and a simple construction. Another object of the invention is to improve rigidity of a support member on which a force acts from a tensioner shoe, a further object of the inventions is to prevent falling of the tension shoe in the width direction thereof, and the other object of the invention is to lubricate a sliding part for improving durability of the tensioner device.
The present invention provides a tensioner device including a support member provided on an engine main body, a tensioner shoe coming into sliding contact with a transmission endless flexible member having a base end section held by the engine main body and a tip end section supported by the support member so as to slide, and a spring pressing the tensioner shoe against the endless flexible member elastically, wherein the support member is formed integrally with the engine main body, and the tip end section is supported touching a guide surface formed on the support member so as to slide.
According to the invention, the support member supporting the tip end section of the tensioner shoe is formed integrally with the engine main body to reduce the number of parts, and the support member can be formed concurrently with the engine main body to reduce the cost. The support member is formed with only a guide surface coming into sliding contact with the tip end section and has no moving portion, so that the construction is simplified and the durability is improved.
Since the guide surface is formed on the support member which is formed integrally with the engine main body, there is no attachment error between the engine main body and the support member and positional relation between the guide surface and the tensioner shoe is set accurately, so that a tensioner device with good tension adjusting function having no substantial deflection for every engine can be obtained.
The tip end section can be set on the guide surface concurrently with attachment of the tensioner shoe to the engine main body, so that the tensioner device can be installed in the engine easily.
In the above-mentioned tensioner device, the support member may have a reinforcement section provided substantially along line of force acting on the guide surface of the support member from the tip end section.
Since force acting on the support member from the tip end section is received by the reinforcement section, rigidity of the support member can be raised to effect a stable tension adjusting function. Further, since the reinforcement section supports the majority of the force acting on the support member from the tip end section, a part of the support member hardly contributing to raise the rigidity can be made thin to make the engine light.
In the above-mentioned tensioner device, a projection for regulating displacement of the tensioner shoe in a width direction thereof by touching the tip end section may be provided on at least one of members positioned on both sides of the tip end section in the width direction.
The displacement of the tensioner shoe in the width direction, which is caused by movement of the endless flexible member since the tip end section slides on the guide surface, can be made minute by the tip end section touching the projection of the member positioned on a side of the tip end section in the width direction. Therefore, it is possible to prevent falling down of the tensioner shoe, and a stable tensioner function can be exhibited. Further, since the projection can be formed utilizing a member positioned in the neighborhood of the tip end section, for example a case covering the endless flexible member, or the engine main body, the falling down of the tensioner shoe can be prevented without increasing the number of parts. When the tensioner shoe with the base end section held by the engine main body is displaced, displacement is largest at the tip end section. According to this invention, displacement of the tensioner shoe is regulated at the tip end section, therefore displacement of the entire tensioner shoe can be made minute easily.
In the above-mentioned tensioner device, a projection for regulating displacement of the tensioner shoe in a width direction thereof by touching a member opposite to a side face of the tip end section may be provided on at least one of both sides of the tip end section in the width direction.
The displacement of the tensioner shoe, which is caused by movement of the endless flexible member since the tip end section slides on the guide surface, can be made minute by the projection on a side of the tip end section in the width direction touching the member opposite to the side of the tip end section. Therefore, it is possible to prevent falling down of the tensioner shoe, and a stable tensioner function can be exhibited. Further, since the projection is formed at the tip end section, the falling down of the tensioner shoe can be prevented easily even if the tip end section is in any position. When the tensioner shoe with the base end section held by the engine main body is displaced, displacement is largest at the tip end section. According to this invention, displacement of the tensioner shoe is regulated at the tip end section, therefore displacement of the entire tensioner shoe can be made minute easily.
Further, in the above-nebtioned tensioner device, the guide surface may have an upper guide surface portion extending upward from a touching position of the guide surface and the tip end section, a surface of the tip end section opposite to the guide surface may have an upper opposite surface portion extending upward from the touching position, and the upper guide surface portion and the upper opposite surface portion may form a space widened toward above to guide lubricating oil flowing onto the upper guide surface portion and the upper opposite surface portion to the touching position.
Lubricating oil flowing down from the above is caught in the widened space, and supplied to the touching section along the upper guide surface portion and the upper opposite surface portion for lubricating the touching position, so that abrasion of the support member and the tip end section can be reduced. As the result, durability of the support member and the tip end section can be improved, and a proper tension adjusting is possible over a long period of time.
In this description, the engine main body means at least one member among a cylinder block, a cylinder head, a crankcase, a cover to be attached to any one f the above members and a housing for an instrument to be driven by the engine which is integral with the cylinder block, the cylinder head, the crankcase or the cover by fixing or forming.